Journal of Current Glaucoma Practice, September-December 2016;10(3):85-90. 85. JOCGP ... Corresponding Author: Mafalda Mota, Resident, Department.
10.5005/jp-journals-10008-1207 Macular Thickness Assessment in Patients with Glaucoma and Its Correlation with Visual Fields
Macular Thickness Assessment in Patients with Glaucoma and Its Correlation with Visual Fields 1 6
Mafalda Mota, 2Fernando T Vaz, 3Mário Ramalho, 4Catarina Pedrosa, 5Maria Lisboa Paulo Kaku, 7Florindo Esperancinha
Aim: To determine the relationship between macular thickness (MT) and visual field (VF) parameters, as well as with changes in the retinal nerve fiber layer (RNFL) thickness in patients with glaucoma and ocular hypertension (OH).
Glaucoma is a multifactorial chronic optic neuropathy characterized by a gradual loss of retinal ganglion cells together with its axons, the retinal nerve fiber layer (RNFL), leading to typical morphological changes in the optic nerve and possible modification of the visual field (VF). If not detected and treated in early stages, glaucoma might result in irreversible blindness.1-3 It is known that structural damage with loss of retinal ganglion cells and their axons precedes functional damage, manifested by typical VF alterations.4,5 Structural loss may occur over 5 years before the onset of functional damage, and it is thought that a 35 to 50% loss of RNFL is necessary for alterations in the VF to be detected.1 Considering the time lapse between structural and functional damage, it is important to develop a strategy that would allow earlier detection of glaucoma. About 30 to 50% of retinal ganglion cells are located in the macular area, where these cells are arranged in parallel below the nerve fiber layer (NFL) and correspond to 30 to 35% of the macular thickness (MT).1,6 The NFL consists of axons from ganglion cells, glia cells, and astrocytes. This layer becomes thicker as it approaches the optic disk, being the largest layer of the peripapillary retina.6 In glaucoma patients, decrease of MT might be attributed to the death of ganglion cells and its axons, ultimately resulting in a decrease in both layers. Increased resolution imaging with fine detail of retinal layers is now possible using spectral domain optical coherence tomography (SD-OCT). This technique enables macula and peripapillary RNFL analyses, being a valuable asset in diagnosing and monitoring glaucomatous disease. Spectral domain optical coherence tomography is a noninvasive and a no-contact exam widely used for the detection of retina alterations. Several studies have tried to develop strategies based on structural defects and their correlation with functional defects, to predict and prevent the deterioration of VF in glaucoma patients.7 Therefore, this is an area of current research and with enormous potential and benefits for patients with glaucoma. In this study, we propose to evaluate whether MT is correlated with VF parameters as well as with RNFL changes, in patients with glaucoma and ocular hypertension (OH).
Materials and methods: Cross-sectional statistical analysis of spectral domain optical coherence tomography (SD-OCT) compared with several VF parameters (mean defect – MD and loss variance – LV), in a nonrandom sample of 70 eyes from patients with glaucoma or OH. Statistical analysis was performed using Statistical Package for Social Sciences®. The correlation coefficient used was determined by Spearman correlation and the value of p